Thomas Flahive had been hospitalized for a few weeks after he was bitten by a mosquito while vacationing in Wisconsin.
He went into a coma and suffered irreversible brain damage.
He died Thursday night at Lutheran General Hospital in Park Ridge.
Flahive's family is donating portions of his body to research the West Nile Virus.
The veteran firefighter was assigned to a firehouse at Milwaukee and Laramie, where his friends are sharing memories of him.
"It's going to be tough," said Asst. Deputy Fire Commissioner Mark Neilson. "We'd been warned about it, that Tom probably wouldn't make it, but it's hard to grasp. Some of the younger guys in this house, Tom is the only officer that they know."
"You hear about it on the news and you hear about all the cases recently, and it really hits home when it's someone that you know," said Lt. Darnell Pettis. "To hear his voice brings a smile to your face. A very good guy. His men loved him. There wasn't anything they wouldn't do for him."
You hear about it on the news and you hear about all the cases recently, and it really hits home when it's someone that you know
Flahive is survived by his wife and three children. He was 58 years old.